A typical fuel cell has a stacked structure comprising a number of stacked power generating elements (or membrane-electrode assemblies) each having an electrolyte membrane sandwiched by electrodes. Because a fuel cell collects electrical power generated by the individual generating elements and supplies it to an external load, it is desirable that the individual generating elements be able to generate an electrical power in a uniform manner. To this end, there has been proposed recovery processes whereby, if a significant decline in generating capacity of some portion of the generating elements has been detected, the output of the entire fuel cell will be restricted so that this portion of generating elements can recover (see inter alia JP2005-197008A and JP2002-164065A).
It is furthermore desirable in a fuel cell to maintain the electrolyte membrane in an appropriately hydrated state during continuous generation of electricity. If a fuel cell continues to generate electricity when the electrolyte membrane has become dry, there is a possibility that the electrolyte membrane will become degraded. However, even if the electrolyte membrane has reached a condition of dryness that could potentially lead to such degradation, if no decline in generating capacity sufficient to trigger the recovery process is detected, the fuel cell will continue to generate electricity, which may result in degradation of the fuel cell. To date, there exist no sufficient measures for addressing this problem.
It is accordingly one object of the present invention to provide technology for suppressing degradation of a fuel cell.